This invention relates to surgical fasteners (e.g., staples), and more particularly to surgical fastener members which are absorbed by the body at an increased rate.
Surgical fastening devices allow a surgeon to fasten body tissue by applying surgical fasteners. The fasteners may be applied singly in succession or a number may be applied simultaneously. Surgical fasteners are often made of metals such as tantalum or stainless steel, which are inert. Fasteners of magnesium, which fasteners are gradually absorbed by the body, are also known.
Non-metallic fasteners are also known and may in some cases have certain advantages over metal fasteners. For example, metal fasteners in the body may scatter X-rays and may therefore degrade the quality of radiographs.
This problem does not arise with fasteners of non-metallic resinous materials. Such resinous surgical fasteners are usually made of two parts: a fastener member which pierces the tissue from one side and a retainer member which interlocks with the fastener member on the other side of the tissue. As used herein, the term "resinous materials" means non-metallic materials, such as natural or synthetic polymers and resins, including protein-based materials, which are relatively flexible and elastic, and which are absorbable by the body. One resinous fastener structure and apparatus for applying it are disclosed in Green U.S. Pat. No. 4,402,445, issued Sept. 6, 1983, which is hereby incorporated by reference in its entirety.
It is generally desirable to eliminate absorbable fasteners from the body promptly. On the other hand, absorbable fasteners must be absorbed slowly enough to retain their tensile strength for a time sufficient to allow the fastened tissue to heal. Desirably the fasteners are also stiff enough to penetrate tissue without the aid of metal assist pins or the like in the fastener-applying apparatus.
Thus, the need exists for resinous fasteners having an increased rate of absorption in the body, but with sufficient retention of tensile strength during absorption and with sufficient columm stiffness to penetrate tissue without buckling.